The field of the present invention is pumps and actuators for pumps which are air driven.
Pumps having double diaphragms driven by compressed air directed through an actuator valve are well known. Reference is made to U.S. Pat. Nos. 5,957,670; 5,213,485; 5,169,296; and 4,247,264; and to U.S. Pat. Nos. Des. 294,947; 294,946; and 275,858. These air driven diaphragm pumps employ actuators using feedback control systems which provide reciprocating compressed air for driving the pumps. Reference is made to U.S. Patent Application Pub. No. 2005/0249612 and to U.S. Pat. No. 4,549,467. Another mechanism to drive an actuator by solenoid is disclosed in U.S. Pat. No. RE 38,239. The disclosures of the foregoing patents and patent application publication are incorporated herein by reference.
Other pumps may be driven by the same actuators but use other arrangements of operatively opposed air actuating chambers to drive a reciprocating pumping mechanism. Pistons with ring seals in a cylinder are also known for the provision of operatively opposed air chambers. Reference is made to U.S. Pat. No. 3,071,118. The disclosure of this patent is also incorporated herein by reference.
Common among the disclosed devices in the aforementioned patents directed to air driven diaphragm pumps is the presence of an actuator housing having air chambers facing outwardly to cooperate with pump diaphragms. Outwardly of the pump diaphragms are pump chamber housings, inlet manifolds and outlet manifolds. Passageways transition from the pump chamber housings to the manifolds. Ball check valves are positioned in both the inlet passageways and the outlet passageways. The actuator between the air chambers includes a shaft running therethrough which is coupled with the diaphragms located between the air chambers and pump chambers. A vast variety of materials of greatly varying viscosity and physical nature are able to be pumped using such systems.
Actuators for air driven pumps commonly include an air valve which controls flow to alternate pressure and exhaust to and from each of the air chambers, resulting in reciprocation of the pump. The air valve is controlled by a pilot system controlled in turn by the position of the pump diaphragms or pistons. Thus, a feedback control mechanism is provided to convert a constant air pressure into a reciprocating distribution of pressurized air to each operatively opposed air chamber.
Actuators defining reciprocating air distribution systems are employed to substantial advantage when shop air or other convenient sources of pressurized air are available. Other pressurized gases are also used to drive these products. The term “air” is generically used to refer to any and all such gases. Driving products with pressurized air is often desirable because such systems avoid components which can create sparks. The actuators can also provide a continuous source of pump pressure by simply being allowed to come to a stall point with the pressure equalized by the resistance against the pump. As resistance against the pump is reduced, the system will again begin to operate, creating a system of operations on demand.
In using such actuators to drive such pumps, greatly varying demands can be experienced. Viscosity of the pumped material, suction head or discharge head and desired flow rate impact operation. Typically the source of pressurized air is relatively constant. Consequently, pump operation finds maximum flow limited by such things as suction and pressure head and fluid flow resistance. Below the maximum capability of the pump, flow rate, including a zero flow rate with the pump still pressurized, has been controlled through restrictions in the output of the pump. Tuning of the actuator exhaust relative to the inlet has also been used for permanent pump efficiency settings.
It remains that control of either the output of the pump or the exhaust of the actuator can alter the performance of the pump to achieve desired flow rates below the maximum but such control does not address both efficient operation and variation in demands placed on the pump.